- De Havilland Canada Dash 7
name= "Dash 7"
caption=Dash 7 in Voyageur Airways colours at the Winnipeg International Airport, 2005.
de Havilland Canada
27 March 1975
3 February 1978
primary user= Various airlines
Canadian Forces United States Army Venezuelan Navy
developed from = DHC-6 Twin Otter
variants with their own articles =
de Havilland Canada Dash 8
The de Havilland Canada DHC-7, popularly known as the Dash 7, is a
turboprop-powered regional airlinerwith STOLcapabilities. It first flew in 1975 and remained in production until 1988 when the parent company, de Havilland Canada, was purchased by Boeing.
Design and development
In the 1960s, de Havilland Canada was already well known worldwide for their series of high-performance
STOLaircraft, notably the very popular Twin Otter. However, these aircraft were generally fairly small and served outlying routes, as opposed to the main regional airliner routes which were already well served by larger, higher-performance aircraft such as the Handley Page Jetstreamand Fokker F27.
The de Havilland Canada company felt they could compete with these designs in a roundabout way. With their excellent STOL performance, their designs could fly into smaller airports more centrally located in city centers, with runways that the other aircraft could not easily use. The original specification called for a 40-passenger aircraft with a fairly short range of 200 statute miles, operating from runways only 2,000 ft long.
With new noise restrictions coming into effect throughout the 1970s, an aircraft tailored for this role would also have to be very quiet. To meet this restriction, the new design used oversized propellers geared to spin at a slower speed than normal; much of the sound from a propeller is generated at the tips which are spinning near the speed of sound, and therefore, by reducing the number of RPM, this noise is reduced substantially. The Dash 7 often landed with only 900 rpm, and took off at only 1,200.
In other respects, the new DHC-7 was essentially a larger, four-engine version of the Twin Otter. The general layout remained similar, with a large T-tail intended to keep the elevator clear of the propwash during takeoff, a high aspect ratio high-mounted wing, and most details of the cockpit and nose profile. Changes included the addition of cabin pressurization which required a switch to a fuselage with a circular cross-section and landing gear that folded forward into the inner engine nacelles.
Most of the rear wing was spanned by a complex double
Fowler flaparrangement for high low-speed lift. The Twin Otter also included "flapperons" that drooped the ailerons as part of the flaps, but these were removed due to safety concerns. Instead the ailerons were reduced in size to allow more flap area, and were so small that they had to be aided by spoilers. On touchdown, hydraulic pressure was automatically reduced in the flaps, allowing them to "blow back" to the 25% position and thus "drop" the aircraft to the runway for better braking performance. The flaps would also "blow back" when engine power was increased during a go-around.Fact|date=November 2007 The four-engine layout aided lift at low speeds due to the wide span of the propellers blowing air over the wing. When reverse thrust was selected on landing, the props "stole" airflow from the wing, further decreasing lift and increasing the effectiveness of the brakes. More importantly, if an engine failed, the asymmetric thrust was much less than on a twin-engine layout, thereby increasing safety and allowing for a lower minimum control speed with an engine inoperative (Vmc). The engines could actually produce drag in flight at idle speed, allowing fine control of the glide slope.
Development started in 1972 and the prototype first flew on
27 March 1975. Testing went smoothly, and the first delivery took place to Rocky Mountain Airways on 3 February 1978. One hundred were delivered by 1984, when the production line was put on hold in favour of the Dash 8. Another 13 were delivered between 1984 and 1988, when the production lines were removed when Boeingbought the company.
The original Series 100 represents the vast majority of the aircraft delivered, and came in two models; the -102 passenger version and -103
combiwith an enlarged cargo door. These were followed by the Series 110 which met British CAA requirements, including the -110 and -111, and finally the Series 150 which included additional fuel tankage and an improved interior in the -150 and -151. There were plans for a Series 200 with the new PT6A-50/7 engines which improved hot-and-high power, but these plans were shelved when Boeing ended production of the design.
The mixture of features on the Dash 7 met with limited commercial success. Most turboprop operators used them as feederliners into large airports, where the STOL performance wasn't considered important. In comparison to other feederliners, the Dash 7's four engines required twice the maintenance of a twin-engine model, thereby driving up operational costs. Finally, those airports that did require a high performance STOL operation were generally small and well served by the Twin Otters; had the airport needed a larger plane to serve its customer base, they would have built larger runways. One exception to this was operations at
London City Airportwhich, upon opening in 1987, was capable of handling few aircraft types besides the Dash 7.
The Dash 7 also gained a number of military orders. The first of these was for two aircraft for the Canadian Armed Forces, who needed them to transport high ranking passengers and freight around Europe. These aircraft received the CF designation CC-132 and were delivered to No.412 Squadron at Lahr, in West Germany. [cite web |url= http://www.airforce.forces.gc.ca/site/equip/historical/dash7lst_e.asp|title= de Havilland CC-132 Dash 7|accessdate= 2008-08-27|date= 2004-04-06|work= Canada's Air Force|publisher=
United States Armyoperates several Dash 7 aircraft as surveillance platforms with the designation EO-5C (RC-7B before 2004) [ [http://www.designation-systems.net/usmilav/nonstandard-mds.html#_MDS_RC7B Non-Standard DOD Aircraft Designations] ] under the Airborne Reconnaissance Low program.
The executives at de Havilland realized they had simply misread the market and ended production in 1988. Fact|date=December 2007 Learning from their mistakes,Fact|date=December 2007 de Havilland started the design of a much more "conventional" twin-engine design in 1978, the extremely popular Dash 8. The DHC-7 production line eventually delivered 113, of which four have been lost and one scrapped. Many of the rest remain in service.
Accidents and incidents
The de Havilland Canada DHC-7 has been involved in six accidents with a total of 68 fatalities. [ [http://aviation-safety.net/database/type/type.php?type=183 Aviation Safety Network Database - de Havilland Canada DHC-7] ]
12 September 2008, a total of 68 Dash 7 aircraft (all variants) remain in airline service. [http://www.ch-aviation.ch/aircraft.php?&search=search&operator=AND&ac_ac=DHC-7&start=0]
Arkia Israel Airlines(8)
Aviones Comerciales de Guatemala (Avcom)(1)
British Antarctic Survey(1)
Linea Turistica Aerotuy(1)
Pelita Air Service(6)
Petroleum Air Services(5)
Regional Air Services (Tanzania)(1)
Trans Capital Air(5)
United States Army(11)
Other civilian operators
British Antarctic Survey(BAS) operates a single Dash-7 in support of its research program in Antarctica. The aircraft undertakes regular shuttle flights between either Stanley on the Falkland Islands, or Punta Arenas in Chile, and the Rothera Research Stationon Adelaide Island. It also operates to and from the ice runway at the Sky Blu Logistics Facility on the Antarctic mainland. [ [http://www.antarctica.ac.uk/living_and_working/aircraft_and_vehicles/aircraft/index.php "Aircraft in Antarctica."] British Antarctic Survey. Retrieved: 31 December 2007.] Kaiken Líneas Aéreas also operated one Dash-7 between Tierra del Fuego and Santa Cruz, in Argentina.
United States Army(10);VEN
plane or copter?=plane
jet or prop?=prop
length main=80 ft 7¾ in
length alt=24.58 m
span main=93 ft 0 in
span alt=28.35 m
height main=26 ft 2 in
height alt=7.98 m
area main=860 ft²
area alt=80 m²
empty weight main=27,650 lb
empty weight alt=12,540 kg
loaded weight main=
loaded weight alt=
max takeoff weight main=44,000 lb
max takeoff weight alt=20,000 kg
Pratt & Whitney Canada PT6A-50
type of prop=
number of props=4
power main=1,120 shp
power alt=835 kW
max speed main=235 knots
max speed alt=271 mph, 436 km/h
range main=700 nm
range alt=770 mi, 1,400 km
ceiling main=21,000 ft
ceiling alt=6,400 m
climb rate main=
climb rate alt=
de Havilland Canada DHC-6 Twin Otter
de Havilland Canada Dash 8
List of airliners
* [http://members.aon.at/~slenz/dash7.html The Dash 7 Homepage]
* [http://www.xdh.ca/DHC_Aircraft/DHC-7/dhc-7.html de Havilland DHC-7 Dash-7]
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